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參數資料
| 型號： | L4916 |
| 廠商： | 意法半導體 |
| 英文描述： | VOLTAGE REGULATOR PLUS FILTER |
| 中文描述： | 穩(wěn)壓器和過濾器 |
| 文件頁數： | 4/8頁 |
| 文件大?。?/td> | 80K |
| 代理商： | L4916 |
Figure2 :
P.C.Boardand ComponentLayoutof Fig. 1 (1 : 1scale).
PRINCIPLE OF OPERATION
During normal operation (input voltage upper than
V
I MIN
= V
OUT NOM
+
V
I/O
). The device works as a
normalvoltageregulatorbuiltaroundtheOP1of the
blockdiagram.
The series pass element use a PNP-NPN connec-
tionto reducethedropout.Thereferencevoltageof
theOP1isderivedfromaREFthroughtheOP2and
Q3, actingas an active zenerdiode of valueV
REF
.
Inthisconditionthedeviceworksin therange(1) of
thecharacteristicof the nonlinear drop controlunit
(seefig.3).
The outputvoltageis fixedto its nominal value:
R1
V
OUT NOM
= V
REF
(1+
) =
R2
R1
R2
V
CFT
(1 +
)
R1= INTERNALLYFIXED RATIO= 2.4
R2
The ripple rejection is quite high (70 dB) and inde-
pendentfrom C
FT
value.
Ontheusualvoltageregulators,whentheinputvol-
tage goes below the nominal value, the regulation
transistors (series element) saturate bringing the
system out of regulation making it very sensible to
everyvariationof theinputvoltage.Onthecontrary,
a control loop on the L4916 consentsto avoid the
saturation of the series element by regulating the
valueofthereferencevoltage(pin2).In fact,when-
ever the input voltage decreases below V
I MIN
the
supervisor loop, utilizing a non linear OTA, forces
the reference voltage at pin 2 to decrease by dis-
chargingC
FT
. So,during thestatic mode,whenthe
input voltage goes below V
MIN
the drop out is kept
fixed to about 1.6V. In this condition the device
worksasalowpassfilterintherange(2)of theOTA
characteristic. The ripple rejection is externallyad-
justableactingon C
FT
asfollows:
V
I
(jw)
SVR(jw) =
=
V
out
(jw)
10
-6
1 +
gm
R1
(1 +
)
jwC
FT
R
2
Where:
gm =2. 10
-5
-1
=OTA’Stypicaltransconductance
valueon linearregion
R1
= fixed ratio
R2
C
FT
= valueof capacitorin
μ
F
The reactiontimeof the supervisorloopis givenby
thetransconductanceof theOTAandbyC
FT
.When
the valueof the ripplevoltageis sohigh and its ne-
gativepeak is fast enoughto determinean istanta-
neous decrease of the dropouttill 1.2 V, the OTA
works in a higher transconductance condition
[range (3) of the characteristic] and discharge the
capacitorrapidously.
If the ripple frequencyis high enoughthe capacitor
won’t chargeitself completely, and the outputvolt-
agereachesasmallvalueallowinga betterripplere-
jection; the device’s again working as a filter (fast
transientrange).
WithC
FT
=10
μ
F;f=100HzaSVRof35isobtained.
L4916
4/8
相關PDF資料 |
PDF描述 |
|---|---|
| L4918 | VOLTAGE REGULATORS PLUS FILTER |
| L4920 | Very Lowdrop Adjustable Regulators(低壓差輸出可調穩(wěn)壓器) |
| L4921 | Very Lowdrop Adjustable Regulators(低壓差輸出可調穩(wěn)壓器) |
| L4922 | Very Lowdrop Adjustable Regulators(帶復位的低壓差穩(wěn)壓器) |
| L4923 | Low Drop Regulator With Reset and Inhibit(帶禁止和復位的低壓差穩(wěn)壓器) |
相關代理商/技術參數 |
參數描述 |
|---|---|
| L4918 | 功能描述:線性穩(wěn)壓器 - 標準 8.5V 0.25A w/Filter RoHS:否 制造商:STMicroelectronics 輸出類型: 極性: 輸出電壓:1.8 V 輸出電流:150 mA 負載調節(jié): 最大輸入電壓:5.5 V 線路調整率: 最大工作溫度:+ 125 C 安裝風格:SMD/SMT 封裝 / 箱體:SOT-323-5L |
| L492 | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:THYRISTOR MODULE|SCR|DUAL|INDEPENDENT|240V V(RRM)|22A I(T) |
| L4920 | 制造商:SGS Thomson 功能描述:LDO Regulator Pos 1.25V to 20V 0.8A 5-Pin(5+Tab) PENTAWATT |
| L4921 | 制造商:STMICROELECTRONICS 制造商全稱:STMicroelectronics 功能描述:VERY LOWDROP ADJUSTABLE REGULATORS |
| L4922 | 制造商:STMICROELECTRONICS 制造商全稱:STMicroelectronics 功能描述:VERY LOW DROP REGULATOR WITH RESET |
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